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Wednesday, April 6, 2011

Flatland Snowmelt

Even from the snowy surface, you can see that melting has started in some places.

In GriggsDakota we are watching the culverts. They must be open to allow water to flow off the land. In some spots that requires the attention of a backhoe.

Culverts, which are drainage passages under our roads and trails, freeze during the winter. You can see that the snow has been removed from the end of the one in the center of this photo.

The water is running here and I believe Spring will take the upper hand. Winter will recede, but we have many days of melting ahead. On our flat land, a slow melt is what we hope for. Melting temperatures during the day and freezing temperatures at night will result in the least damage to the land and everything else. So far, that is what is happening here.

I ventured into nearby GreaterDakota to find some better examples of melting on the land. Here the water is running down into a ditch from a flat field. The water is pooling somewhat on the field, but seems to be flowing adequately into the ditch by the road.

Roadside ditches are important to controlling the flow of water off the fields. They become waterways and the roads themselves are often dams to keep things under control.

With a slow melt, even our heavy snowpack can be handled. The surface will freeze overnight, thaw during the morning, and flow for 6-10 hours before freezing again.

Streams form in the low spots of the fields as water always seeks the lowest point, but the flow stops with an overnight freeze. The larger streams and rivers continue to flow overnight. The more slowly the water is added to the flow, the less flooding there will be downstream.

Even in this area, where the melt is further along than in GriggsDakota, there is plenty of snow yet to melt. We do wish for warm Spring temperatures, but only after a slow Spring melt.

It is very difficult to predict how much flooding we will face in the coming days. Notice this beautiful coulee with a bridge over it.

In the above photo, taken from the bridge, it is nearly full and water is still flowing into it.

This photo, taken across the bridge in the opposite direction shows an ice dam which is stopping the flow out of the coulee. The dam will either break free and empty the coulee or the bridge will be closed soon. Someone is monitoring it.

The water is flowing from the field to an open culvert.

Water is also flowing from the ditch and the flow out is controlled by the culvert.

If the culverts cannot handle the flow, are plugged with ice, or there is an ice jam as illustrated above, the water will quickly back up and flow over the road. That is why we caution people not to drive on unfamiliar roads during the Spring melt. And never try to drive through water over the road as rural roads wash out easily. You might lose your car or worse.